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I remember seeing a question with an accepted answer nearly identical to mine. However I cannot find it so I've answered your question for now, at least until someone stumbles across the link.
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jw013Apr 5 '12 at 7:41

While the answers are the same, the questions are rather different. That one is "I have a tool, but what's it good for?" and this one is "I have a problem, what tool should I use?" It's probably worth keeping both.
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cjmApr 5 '12 at 8:14

Under Linux, you can use the rename utility (called rename.ul under Debian, Ubuntu and derivatives) to change a part of the file name (which can be in the directory part). rename foo bar path/to/file changes the first occurrence of foo in path/to/file to bar. If a file name doesn't contain the first string, the file is left in place.